US2686554A - Molding method - Google Patents

Molding method Download PDF

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US2686554A
US2686554A US232683A US23268351A US2686554A US 2686554 A US2686554 A US 2686554A US 232683 A US232683 A US 232683A US 23268351 A US23268351 A US 23268351A US 2686554 A US2686554 A US 2686554A
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United States
Prior art keywords
mold
tread
core
stresses
tire
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US232683A
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English (en)
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Dorr J Hinman
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Uniroyal Inc
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United States Rubber Co
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Priority to BE511522D priority Critical patent/BE511522A/xx
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Priority to US232683A priority patent/US2686554A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D30/00—Producing pneumatic or solid tyres or parts thereof
    • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
    • B29D30/0601—Vulcanising tyres; Vulcanising presses for tyres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/32—Component parts, details or accessories; Auxiliary operations
    • B29C43/54—Compensating volume change, e.g. retraction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D30/00—Producing pneumatic or solid tyres or parts thereof
    • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D30/00—Producing pneumatic or solid tyres or parts thereof
    • B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
    • B29D30/52—Unvulcanised treads, e.g. on used tyres; Retreading
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2021/00—Use of unspecified rubbers as moulding material

Definitions

  • This invention relates to an improved method for shaping rubber and similar materials having a high elastic memory, and more particularly the invention relates to an improved molding method involving the step of producing stresses in the molded material to counteract distorting stresses normally present therein.
  • One object of the invention is to provide a method for molding rubber and the like which can be carried out more rapidly and more economically than previous molding methods.
  • Another object is the provision of a method for counteracting undesirable strains which are normally imparted to rubber and similar materials having high elastic memory when they are molded.
  • Still another object is to provide an improved method of making pneumatic tires by compression molding.
  • Still a further object of the invention is a provision of a method of forming tire treads which insures that the tread will be uniform around the circumference of the tire, thereby eliminating the thump, imbalance, and undesirable riding characteristics sometimes encountered in pneumatic tires in which the tread portion has been formed by conventional methods.
  • Fig. l is a largely schematic side elevational View of an apparatus for preforming the rubber tire tread in accordance with one method of oarrying out the invention
  • Fig. 2 is a transverse sectional elevational view, taken along the line 2 2 of Fig. l, oi' a preformed tire tread split longitudinally into two Vequal sections;
  • Fig. 3 is a partial elevational view of a molding press in the open position, with parts shown in section, for molding the preform;
  • Fig. 4 is a similar view of the molding press of Fig. 3 in the ⁇ closed position;
  • Fig. 5 is a similar view of the molding press in the open position with a tire carcass' containing a 'curing bag in process of'being inserted in the mold;
  • Fig. 6 is a similar fragmentary View showing the molding press in the closed position for uniting the formed tread to the tire carcass;
  • Fig. 7 is a transverse sectional elevational view showing the united tread and carcass being inserted in a nal shaping and curing mold;
  • Fig. 8 is a transverse sectional elevational View of the shaping and curing mold with the tire in place for nal shaping and vulcanization;
  • Fig. 9 is a transverse sectional elevational View of the completed tire.
  • Fig. 10 is a diagrammatic perspective View of a portion of a molded prefrom showing the stresses imparted thereto during the process of the invention.
  • Figs. 11 and A12 are vector diagrams of stresses occurring during the process.
  • the invention provides an improved method of impressing a desired shape, as by molding, upon materials having substantial elastic memory,that is, materials which are particularly rubbery so that they have a marked tendency to resist the shaping forces imposed upon them and tend to recover or return to some former ⁇ shape which they had prior to the shaping operation.
  • Such behavior is characteristic not only of raw natural rubber itself, but is exhibited also by the typical synthetic rubbers, notably those derived by polymerization of conjugated dienes,e. g., Buna-S, the rubbery copolymer of styrene and butadiene-1,3; polychloroprene, etc.
  • the mold may be opened without fear of shrinkage and distortion of the molded form.
  • the fact that cooling of the rubber .in the mold results in such freezing of the shrinkage ⁇ stresses' is confirmed by the interesting observation that if the molded object so produced is heated to an elevated temperature at a later time, .shrinkage and distortion of the object will take place, due to release of the frozen stresses. It will be understood that this phenomenon is peculiar to rubber in the raw or unvulcanized state only; if
  • the rubber is vulcanized such elastic memory forces'no longer exist.
  • the necessity for cooling the mold before opening it in order to avoid shrinkage and distortion gives rise to delay in manufacturing operations, particularly in the case of such articles as heavy service pneumatic tires, wherein the molds are necessarily of great size and may require considerable 4time for cooling.
  • delay signincantly reduces the amount of production which can be obtained from a given piece of molding equipment.
  • the cooling operation represents a substantial wastage of heat, since the mold must be heated up again preparatory to a subsequent molding operation.
  • the present invention makes the cooling procedure unnecessary, and is based on the discovery that shrinkage of the shaped form can be prevented by producing within the molded material additional stresses which counteract the shrinkage stresses.
  • -the desired shrinkage-neutralizing stresses are produced in such annular objects as molded tire treads by exerting a circumferential shearing action on the rubbery material in the mold.
  • shearing action is produced by rotating the core wall in contact with the inner surface of the tread relative lto the mold wall in Contact with the outer surface of the tread, it being understood that there will be suflicient frictional resistance between the surfaces of the tread and the core and mold walls so that such relative rotation produces rotary or circumferential shearing of the rubber mass.
  • the rotary shearing stresses thus produced prevent the normal molding stresses from causing shrinkage, so that the mold can be opened Without cooling.
  • Fig, 1 shows an arrangement of two opposed heated extruding devices l and Il which are adapted to deliver through a common die head l2 two different streams of rubber stock, the one stream I3 being composed of abrasion resistant tread stock, and the other stream le being composed of crack resistant sidewall stock.
  • the exit ori- Y ice l5 of the die I2 has the approximate cross sectional shape of a tire tread assembly, and the streams I3 and l@ are united firmly together as they stream through the die perennial.
  • the tread After emerging from the die the tread may be split longitudinally along its center line by rotating cutting knife I6 as the tread advances in engagement with back-up rollers iT, or may be split by any other practical means to produce two equal tread halves I8 and I9, as indicated most clearly in Fig. 2.
  • the split tread advances onto the rollers '20 of a conveyor, and may be cut transversely at intervals by a rotating knife 2
  • these bands or preforms are usually made slightly undersized and are stretched when applied to the core member so that they cling to and substantially conform to the surfaces of the core members.
  • the preforms are then molded in a mold comprising, as shown in Figs. 3 to 6, upper and lower annular mold halves or shells 2d and 25, each having on its inner face an annular recess 26, 2"! corresponding in outline to the external contour of the tire tread except that the mold surfaces are of essentially smooth contour, that is, no provision is made in the mold surface for forming an anti-skid tread design on the tire surface.
  • a cooperating annular core piece Z8 is adapted to be disposed between the upper and lower mold halves and is provided with upper and lower protruding faces 29, 3B having the approximate contour of a tire carcass.
  • extends outwardly radially at the central plane of the core and is provided with peripheral gear teeth 32 whereby the core may be rotated in a manner to be described.
  • the mold halves are mounted in a suitable press, comprising a lower movable platen 35 on the upper surface of which the lower mold half 2c is mounted, and an upper xed platen 3S on the under surface or which the upper mold half 24 is fixed.
  • the lower platen 35 is adapted to be raised or lowered by the usual double acting hydraulic cylinder 3i contained within the base 3B of the press, from which a piston 39 carrying the platen 35 extends upwardly.
  • Tie rods di) extend upwardly from the base of the machine and pass slidably through the lower platen 35 to support the upper platen 35.
  • One of the preforms i8, IS is stretched over each of the core surfaces 2B, 3B as indicated in Fig. 3 and the mold halves are then brought together against the core piece to enclose the preforms, as indicated in Fig. 4, in mold cavities d2, #i3 each having the shape of a transaxial half of the tire tread. in the closed position, the upper and lower surfaces of the external core flange 3
  • the preforms I8 and I9 are preferably at a suitable elevated temperature, e. g., 200 F., when they are placed on the core piece '28. Ordinarily, the preforms will retain sumcient heat from the previous extrusion operation to be at this temperature but, if not, they may be heated by some external means such as steam or hot air. It is also preferable that the core piece be preheated to an elevated temperature, e. g., 250 F.
  • the mold halves 24, 25 are also preheated to an elevated temperature, e. g., 250 F., as by circulating a heated fluid medium from an external source (not shown) through internal passages 45, 4B in the body of the mold halves.
  • this compression molding operation induces in the rubber stock constituting the preforms I8, I9 definite stresses which are opposite in direction to the strains imposed on the stock in the course of the molding. Asa result of the elastic memory of the stock these stresses tend to persist and will cause the molded form to retract and pull away from the surfaces 26 and 27 of the mold cavity when the mold is opened.
  • a means for rotating the core member 28, comprising a motor 50 mounted on the lower surface of the upper platen 35 in such position that a pinion gear 5I on the end of a shaft extending downwardli7 from the motor engages the peripheral gear teeth 32 of the core piece 28 when the press is closed as indicated in Fig. 4.
  • the motor 50 is a commercially available hydraulic motor and is capable of being rotated in either direction, as desired, at controlled speeds. It is connected to the usual source (not shown) of hydraulic fluid by means of iluid supply lines 52.
  • the'core 28 is rotated with respect to the outer mold shells 24, 25, producing rotary shearing of the rubber stock.
  • the degree of rotation of the core 28 is preferably suicient to produce rotary shearing plastic deformation substantially in excess of the shearing elastic deformation of the rubber stock, that is to say, the stock is subjected to shearing strain beyond the strain that would berecovered elastically if the stock were released.
  • the angular rotation required to produce such shear will of course depend on the ratio of the thickness of the tread at the parting line of the mold to the circumference of the tread. With the mold illustrated, a forward rotation-of 20, equivalent to 1000% shear, followed by al backward rotation of 2, equivalent to 100% shear, was employed with satisfactory results.
  • the step of rotating the mold core with respect to the mold shell makes it possible to carry out the foregoing prefo-rming method more rapidly and economically than has heretofore been pos-l sible since it eliminates the necessity for a cooling step before opening the mold after compressing the preforms as shown in Fig. 4.
  • the core is surfaced in such manner that its adhesion to the rubber stock is relatively small.
  • the core 23 is removed. Thereri's then inserted in the mold a shaped tire carcass 55, containing a curing bag 55, as indicatedV in Fig. 5.
  • the tire carcass 55 may be built up previously in the form of an annular band on a collapsible tire building drum by superimposing a plurality of plies of rubber tirev fabric and incorporating the usual inextensible bead elements in the marginal edges of the band.
  • the band is then shaped into annular toroidal form in a vacuum shaping box and the curing bag 56 is inserted therein.
  • the curing bag ,55 is marde ofV extensible, heat resistant material, such as butyl rubber, and is formed with relativelyV thick Walls having an external contour corresponding to the internal shape of the tire carcass and is provided with an inlet opening l in the rim portion thereof.
  • the mold halves 24, 25 are closed over the assembly of curing bag and carcass, as indicated in Fig. 6, and the bag 56 is inflated through the inlet opening 5l by means of an air hose 58 connected thereto, causing the carcass to expand into contact with and to adhere to the tread segments.
  • the temperature of the tread segments of this stage of the operation will generally be about 250 F., and the temperature of the carcass is usually about 200 F.
  • the elevated temperature of the carcass permits the carcass cords to readjust themselves as the carcass is expanded against the tread segments.
  • the pressureapplied Within the curing bag at this stage Will'be within the range from 60 to 250 p. s. i. Satisfactory results have been obtained by maintaining a pressure of about 90 p. s. i.
  • the contour of the inner surface of the tread be such that the carcass, when it is eX- panded by the action of the curing bag, contacts the tread rst at the bead area, and then at the sidewall, and thereafter progressively up to the center of the crown, to thereby expel all the air from between the mold halves.
  • a contour is obtainable on the interior surface of the tread by suitably shaping the surface of the core piece 28, which determines the contour of the inner tread surface.
  • the mold is thereafter opened, and because of the greater adhesion of the tread to the carcass than to the mold halves, the tread separates from the mold and remains on the carcass. It has been found that satisfactory results are obtained by employing an unpolished chromium plating on the mold surfaces, that a generally matte surfaced chromium. In preparing the mold surfaces they are first vapor blasted and then chrome plated and the surface is left unpolished. The surface thus produced has less adhesion for the rubber than the tire carcass, but at the same time this surface has greater adhesion to the rubber than the polished chrome plating on the core piece 28, so that the tread remains in the mold halves as shown in Fig. 5, rather than on the core when the mold is opened after the preforming operation as indicated in Fig. 4. If desired, the mold surfaces, in place of being unpolished chromium, may be nickel plated, but the nickel plated surface has the disadvantage that it requires occasional polishing to remove oxidized surfaces which causes the rubber to stick to it.
  • tread, carcass and curing bag is now ready for the vulcanising operation, and for this purpose the assembly may then be placed, as indicated in Figs. '7 and 8, in a conventional tire curing mold of the pot heater type composed of upper and lower mold halves 50, 6l which define a tire shaped mold cavity 62 having a design in its'surface forming an anti-skid pattern in the tire tread.
  • a conventional tire curing mold of the pot heater type composed of upper and lower mold halves 50, 6l which define a tire shaped mold cavity 62 having a design in its'surface forming an anti-skid pattern in the tire tread.
  • the tire mold 50, 6l is placed in a vulcanizing press (not shown) wherein it is subjected to heat and pressure suicient to vulcanize the tire tread and carcass. It will be understood that at the same time heat and pressure are applied to the interior of the curing bag through the opening 5l.
  • the mold cavity defined between the preforming mold halves 2d, 25 is somewhat smaller than the nal vulcanizing cavity 52, so that the carcass and tire tread expand somewhat further in the final mold, under the influence of internal pressure in the curing bag.
  • the tread and carcass assembly as shown in Fig. 7 may, if desired, be cured or vulcanized in a conventional unit vulcanizer of the McNeill or De Mattia type.
  • the nnished tire 59- after removal from the mold is shown in Fig. 9.
  • the molding of the tire tread as a preformed shape in the foregoing manner results in a uniform, balanced tread. Because there is no transverse splice in the tread, as is the case in tires made in the conventional manner, a primary cause of the irregularity of the tire is removed and tires of superior quality result.
  • the step of rotating the mold members relative to each other to counteract shrinkage stresses and make the mold cooling step unnecessary results in an appreciable saving of time in the manufacture of tires by the foregoing method.
  • the mold cooling step may require about 3 or 4 minutes, while the present mold rotating method requires no more than about 30 seconds.
  • the mold rotating method described may be applied with equal beneflt to the tire compression molding method described in U. S. Patent 2,497,226, of McNeill, issued February 14, 1950. To apply the present method to the molding process disclosed in this patent it is necessary merely to iix one or the other of the mold members and to rotate the other mold member as described above.
  • the mold rotating step may also be applied to advantage in the tire molding method described in copending application of D. J. Hinman, Serial No. 232,681, led of even date herewith, now Patent No. 2,649,891, in which a tire tread is preformed in the form of a cylindrical'band.
  • the relative rotation of the mold members to produce in the molded rubber a strain pattern which counteracts the strains which are normally set up during the compression molding has further advantages in that it is found that the rotation makes it possible to accomplish molding of the preform without using such great pressures as have heretofore been considered necessary for this purpose. For example, it has formerly been considered necessary to us molding pressures of the order of 2,000 p. s. i. of projected area when molding the raw preforms as illustrated in Fig. 4, but it has been found that when the core is rotated with relation to the mold as described, pressures as low as 300 p. s. i. are quite satisfactory, and in fact, are preferred because less torque is required to rotate the core than when the high forming pressures were used.
  • a further advantage of eliminating the usual cooling step by rotating the core is that when the assembly of tire tread and carcass is placed in the final vulcanizing mold, as indicated in Figs. '7 and 8, it has a higher temperature than it would have if the preforming mold had to be cooled before it could be opened ⁇
  • This increased temperature of the tire as it is placed in the vulcanizing mold makes it possible to realize a saving of the order of 15% on the time of cure. This is possible because the tread is formed at temperatures well above '200 F., and, when retraction stresses are controlled by shear treatment, cure can start immediately when the tire is placed in the curing mold, thus saving time normally required to heat the tread stock up to Y that temperature.
  • the rotary shearing step not only eliminates the effect of residual shrinkage stresses arising in the preformed molding step itself, but also counteracts any distortion stresses present in the preforms it, i9 before they are placed in the mold.
  • distortion stresses may arise, for example, during the extrusion operation depicted in Fig. l, which frequently produces localized areas of stress along the length of the preform due to a surging action in the extruder, and such stresses may also arise as a result of the operation of splicing the preform into the form of an annular band for placing on the surfaces 29 and 3i! of the mold core 28 as depicted in Fig. 3.
  • FIG. 10 This movement of the stock during the preform molding is represented in Fig. 10, where the broken lines show the original shape of the preform it and the solid lines show the iinal shape when the mold is closed. Any plane perpendicular to the core surface cut thru this section of the preform after the molding operation could be illustrated by the rectangle ABCD. Neglecting the curve of the mold and core for purposes of simplicity, the rectangle ABCD appears in the iiat as shown in Fig. ll.
  • Broken line El? represents the position ofr line AB in original shape of the preform.
  • Vector GH (Fig. 11) represents the movement of a point l0 G on line EF during the molding operation.
  • vector HG represents the resulting stress in the opposite direction which tends to return the preform to its original shape. This is the residual stress which normally would cause the stock to pull away from the mold.
  • the rest period provided after the initial rotation of the mold core permits substantial stress decay to set in, so that the magnitude of the initial shearing stresses are greatly reduced.
  • This reverse rotation will therefore be sufficient in magnitude to return the stock to the position which it would take up if permitted to retract of itself along the rotary shear lines.
  • the reverse rotation actually forces the stock to take up in a short time the position which it would attain at a much slower rate if left to itself, due to what may be termed sluggish retraction.
  • the rest interval allowed after the reverse rotation before opening the mold permits the stresses to neutralize so that the stock is in a stateof set" when the mold is opened.
  • the invention is particularly well adapted to use in connection with tire manufacturing operations wherein the tire tread is preformed from raw rubber stock in annular form by molding, and subsequently united to a tire carcass in the same mold.
  • the present invention makes it possible to open the preforming mold without having the molded performed separate from the mold while the previously prepared tire carcass is being inserted in the mold.
  • a method of shaping rubbery plastic materials having a high elastic memory comprising in combination the steps of compressing the material in a desired shape between two confining members while subjectingV the material toheat, moving one conning member with respect to the other to produce shear stresses in the material, maintaining said members in said position for a time suicient for a substantial stress decay to take place, and moving said confining members with respect to each other in a direction opposite to said first movement partially toward their initial position, whereby any retraction stresses present in the material are substantially obliterated.
  • a method of molding annular articles from rubbery plastic materials having a high elastic memory which comprises compressing the material in an annular mold cavity dened between two confining surfaces in a heated plastic state, rotating one confining surface with respect to the other about the principal axis of the annular cavity, to produce rotary shearing stresses in the material, maintaining said surfaces in the rotated position until the greater part of such stress has decayed, and thereafter reversely rotating said surfaces by an amount suiiicient to induce reverse rotary shear of the stresses equal in magnitude to the residual shear stresses remaining from said iirst rotation, and maintaining said surfaces in said reversed position until said reverse rotary shear substantially decays.
  • a method of molding annular articles from rubbery plastic material having a high elastic memory which comprises subjecting the material to pressure in an annular mold cavity dei-ined between two mold members in a heated plastic state, rotating one mold member with respect to the other about the principal axis of the annular cavity to produce rotary shear stress in the material, maintaining said mold members in the rotated position until a major portion of said stress has decayed, and thereafter rotating said mold members in an opposite sense to the initial rotation for an amount sufficient to return the material substantially to the position to which it would return if permitted to retract freely in a rotary direction, and maintaining said members in said last position until rotary shear stress remaining in the material has substantially decayed.
  • a method of molding annular articles from rubbery plastic material having a high elastic memory which comprises subjecting the material to pressure in an annular mold cavity defined between two mold members in a heated plastic state. rotating one mold member with respect to the other about the principal axis of the annular cavity, the said material having sufcient adherence to the mold members so that said rotation produces rotary shear stress in the material, maintaining said mold members in the rotated position until a major portion of said stress has decayed, and thereafter rotating said mold members in an opposite sense to the initial rotation to produce reverse shear in amount substantially of the same order as the residual rotary shear stress remaining after said stress decay, and maintaining said members in said last position until the material is substantially relaxed within the mold cavity.
  • a method of molding pneumatic tire treads from raw rubber stock comprising in combination the steps of disposing an approximate preform of F a tire tread in an annular mold comprised of a shell member and a core member, pressing said shell member and core member together to shape the preform in tire tread form at elevated temperature, rotating the shell member and the core (member relative to each other, the tread having sumcientadhesion to the said core vand shell so that such rotation *a produces rotary shearing stresses within the raw tread, subsequently rotating the shell member and the core member in an opposite sense to produce rotary shearing stresses which neutralize the first mentioned rotary shearing stresses, whereby the tendency of the tread to retract when the mold is subsequently opened is substantially reduced.
  • a method of molding pneumatic tire treads from raw rubber stock comprising in combination the steps of disposing an approximate preform of a tire tread in an annular mold comprised of a shell member and a core member, pressing said shell member and core member together to shape the preform in tire tread form at elevated temperature, rotating the shell member and the core member relative to each other, the tread having sucient adhesion to the said core and shell so Ythat such rotation produces rotary shearing stresses within the raw tread, subsequently rotating the shell and the core relative to each other in an opposite sense from said rst rotation to obliterate the rst mentioned shearing stresses, and thereafter opening the mold, the surface of said core having less adhesion to the tread than the surface of the shell has to the tread, whereby the tread remains in the position in which it was molded within said shell.
  • a method of making pneumatic tires comprising in combination the steps of molding a preform from raw rubber stock in the form of a transaxial half of a tire tread in an annular mold cavity deiined between a core member and a shell member, rotating said core member relative to said shell member, said rubber stock having sufficient adhesion to said core member and said shell member so that said rotation produces rotary shearing strains within the raw rubber stock which substantially obliterate retraction stresses induced in the rubber stock by the molding operation, separating said core member from said shell member, the raw rubber stock having greater adhesion to said shell member than to said core member so that the raw molded tread preform remains within the shell, providing a pneumatic tire carcass, bringing two of such raw molded transaxial halves of the tire tread into contact with said tire carcass, uniting said raw tread halves and carcass under the iniiuence of heat and pressure, and curing the resulting assembly in a tire mold.
  • a method of molding pneumatic tire treads from raw rubber stock comprising shaping the raw rubber stock in an annular mold comprised I3 14 of a shell member and a core member between References Cited in the le of this patent ⁇ VhCh the rubber Stock S molded in tread form at elevated temperature Without curing the tread, rotating the shell member and the core Number Name Date member relative to each other to produce rotary 5 0791584 Hazen et a1 May 41 1937 shearing stresses within the raw tread, and there- 21231369 Merrlu Feb- 11 1941 after opening the mold after the raw rubber tread 21372177 Conner Ma? 27 1940 has substantially relaxed, whereby the tendency 476,884 Maynard July 19) 1949 of the raw tread to retract upon said opening of 21497326 McNelu Feb- 14: 1950

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Tyre Moulding (AREA)
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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2724425A (en) * 1953-06-30 1955-11-22 Us Rubber Co Tire building method
US2764220A (en) * 1954-09-13 1956-09-25 Goodyear Tire & Rubber Method of making a tire
US2860379A (en) * 1954-04-24 1958-11-18 Continental Gummi Werke Ag Method of centrifugally casting vehicle tires
US2868270A (en) * 1955-08-22 1959-01-13 Roscoe L Brown Apparatus for vulcanizing ornamental trim on tire walls
US2873790A (en) * 1953-04-20 1959-02-17 Us Rubber Co Method of making pneumatic tires by casting a liquid polyester-diisocyanate composition
US2906314A (en) * 1954-03-02 1959-09-29 Dunlop Tire & Rubber Corp Pneumatic tires
US2925623A (en) * 1952-05-03 1960-02-23 Continental Gummi Werke Ag Pneumatic tire for vehicles and method of making same
US2990874A (en) * 1957-12-19 1961-07-04 Hawkinson Paul E Co Method of forming a tread on a pneumatic tire casing
US3143155A (en) * 1961-05-29 1964-08-04 Firestone Tire & Rubber Co Tire
US3276930A (en) * 1962-05-11 1966-10-04 Du Pont Tire fabrication process
US3427213A (en) * 1965-08-03 1969-02-11 Sterling Alderfer Co Method for producing molded tires
US3458373A (en) * 1964-12-02 1969-07-29 Bayer Ag Injection-molded,reinforced pneumatic tires and method of making same
DE2164841A1 (de) * 1970-12-29 1972-07-20 Luftreifen und Verfahren zu seiner Herstellung. Anridgestone Tire Co. Ltd., Tokio
US3695808A (en) * 1969-02-04 1972-10-03 Firestone Tire & Rubber Co Apparatus for making tires
US4007069A (en) * 1970-12-29 1977-02-08 Bridgestone Tire Company Limited Process for making radial tires
US4014969A (en) * 1970-08-05 1977-03-29 Semperit Aktiengesellschaft Method of making a molded article with oriented fiber reinforcements
US4122137A (en) * 1975-12-15 1978-10-24 The Firestone Tire & Rubber Company Radiation cure of rubber sheets
US4152388A (en) * 1976-07-19 1979-05-01 Caterpillar Tractor Co. Tire tread forming method
US4239075A (en) * 1977-07-14 1980-12-16 Hedlund John A Profiled tire tread
US4294638A (en) * 1975-02-12 1981-10-13 Rasmussen O B Circular extrusion method providing for rotation around the extrusion opening
US5015315A (en) * 1988-02-27 1991-05-14 Sumitomo Rubber Industries, Ltd. Method of making a pneumatic tire
EP3316724A4 (en) * 2015-07-14 2019-03-06 Qalo LLC COMPRESSION MOLDED SILICONE RING

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US2231769A (en) * 1938-06-22 1941-02-11 Us Rubber Co Method of treating rubber mountings
US2372177A (en) * 1942-01-05 1945-03-27 Colt S Mfg Co Article of manufacture and method of making the same
US2476884A (en) * 1946-10-09 1949-07-19 Prophylactic Brush Co Method for tire manufacture
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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2925623A (en) * 1952-05-03 1960-02-23 Continental Gummi Werke Ag Pneumatic tire for vehicles and method of making same
US2873790A (en) * 1953-04-20 1959-02-17 Us Rubber Co Method of making pneumatic tires by casting a liquid polyester-diisocyanate composition
US2724425A (en) * 1953-06-30 1955-11-22 Us Rubber Co Tire building method
US2906314A (en) * 1954-03-02 1959-09-29 Dunlop Tire & Rubber Corp Pneumatic tires
US2860379A (en) * 1954-04-24 1958-11-18 Continental Gummi Werke Ag Method of centrifugally casting vehicle tires
US2764220A (en) * 1954-09-13 1956-09-25 Goodyear Tire & Rubber Method of making a tire
US2868270A (en) * 1955-08-22 1959-01-13 Roscoe L Brown Apparatus for vulcanizing ornamental trim on tire walls
US2990874A (en) * 1957-12-19 1961-07-04 Hawkinson Paul E Co Method of forming a tread on a pneumatic tire casing
US3143155A (en) * 1961-05-29 1964-08-04 Firestone Tire & Rubber Co Tire
US3276930A (en) * 1962-05-11 1966-10-04 Du Pont Tire fabrication process
US3458373A (en) * 1964-12-02 1969-07-29 Bayer Ag Injection-molded,reinforced pneumatic tires and method of making same
US3427213A (en) * 1965-08-03 1969-02-11 Sterling Alderfer Co Method for producing molded tires
US3695808A (en) * 1969-02-04 1972-10-03 Firestone Tire & Rubber Co Apparatus for making tires
US4014969A (en) * 1970-08-05 1977-03-29 Semperit Aktiengesellschaft Method of making a molded article with oriented fiber reinforcements
DE2164841A1 (de) * 1970-12-29 1972-07-20 Luftreifen und Verfahren zu seiner Herstellung. Anridgestone Tire Co. Ltd., Tokio
US4007069A (en) * 1970-12-29 1977-02-08 Bridgestone Tire Company Limited Process for making radial tires
US4294638A (en) * 1975-02-12 1981-10-13 Rasmussen O B Circular extrusion method providing for rotation around the extrusion opening
US4122137A (en) * 1975-12-15 1978-10-24 The Firestone Tire & Rubber Company Radiation cure of rubber sheets
US4152388A (en) * 1976-07-19 1979-05-01 Caterpillar Tractor Co. Tire tread forming method
US4239075A (en) * 1977-07-14 1980-12-16 Hedlund John A Profiled tire tread
US5015315A (en) * 1988-02-27 1991-05-14 Sumitomo Rubber Industries, Ltd. Method of making a pneumatic tire
EP3316724A4 (en) * 2015-07-14 2019-03-06 Qalo LLC COMPRESSION MOLDED SILICONE RING

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